Nitrogen oxides (NOx) are a combination of nitric oxide (NO) and nitrogen dioxide (NO2) and are a natural byproduct in the combustion of all fossil fuels. NOx is formed when the nitrogen in the air chemically interacts with oxygen released by the combustion process. Sulfur oxides (SOx) are also released during the combustion process. SOx is primarily composed of sulfur dioxide (SO2).
NOx has several deleterious effects. In either its pure chemical or particulate form, NOx is known to present a severe health hazard to the respiratory system. In addition, NOx is the basis for acid rain, which can affect the quality of air, soil, and water and can chemically decompose man-made structures including roads, bridges and buildings. SOx is known to cause respiratory problems, visibility reduction, acid rain and corrosion.
High voltage electron beams (500,000 to 1,000,000 Volts) have been demonstrated to remove up to 90% of the NOx emissions from a coal fired power plant. See “Accelerators for Americas Future,” Symposium Proceedings, Walter Henning and Charles Shank Chairs. Published by US Department of Energy, June 2010.
The process for removing NOx from exhaust gas with electron beams, also called “flue gas,” has been established using a catalytic process in which ammonia and water are injected into the flue gas before the gas is irradiated by a continuous electron beam. The electron beam dissociates the water molecules into free radicals, which then reacts with the NOx to produce nitric acid. The acid is neutralized by the ammonia to produce ammonium nitrate [NH4NO3], which can be used as a fertilizer. See R. Kikuchi and Y. Pelovski, “Low-dose irradiation by electron beam for the treatment of high-SOx flue gas on a semi-pilot scale—Consideration of by-product quality and approach to clean technology,” Process Safety and Environment 87 (2009) 135-143; see also U.S. Pat. No. 5,695,616 to Helfrich et al.
This catalytic process has been demonstrated in pilot coal plants in the US, Japan, Germany, Poland, China, and Russia, see S. Korenev and R. Johnson, “Electron accelerators for cleaning flue gases and for oil liquefaction,” Proceedings of EPAC08, Genoa, Italy 2008. Paper TUPP141; as well as on oil based plants, see A. A. Basfar, O. I. Fageeha, N. Kunnummal, A. G. Chmielewski, J. Licki, A. Pawelec, Z. Zimek, and J. Warych, “A review on electron beam flue gas treatment (EBFGT) as a multicomponent air pollution control technology,” NUKLEONIKA 2010; 55(3):271-277.
The inventors of the present invention previously developed an apparatus and method for catalyst-free removal of NOx from exhaust gases from combustion fuel sources using pulsed electron beams. See U.S. Pat. No. 9,089,815 entitled “Catalyst-Free Removal Of NOx From Combustion Exhausts Using Intense Pulsed Electron Beams,” the entirety of which is hereby incorporated by reference into the present disclosure. One limitation of this previously developed technique is that the NOx is removed a temperatures higher than room temperature. In addition, the prior technique used temporally longer electron beam pulses, which the inventors have found not only require more energy to produce but are not as efficient in the NOx removal process as are shorter pulses. Finally, the previously developed technique required the creation of a magnetic field to direct the electron beam into the gas, which creates complications in fielding of the application due to dimensions and power consumption of the magnet.
The present invention provides an improved technique and apparatus which overcomes these drawbacks of the inventors' previously developed technique.